Humans have shaped the evolution of animals for as long as we've been catching and eating them. In the days of spear hunting, speed and boldness were survival assets. But with today's high-powered rifles, the tables have turned. Animals that speed off in the open are most at risk. And the advantage goes to shyer, more secretive animals. At least among elk. So says a study in the Proceedings of the Royal Society B. [Simone Ciuti et al, Human selection of elk behavioural traits in a landscape of fear]

Researchers outfitted 122 elk with GPS collars, and tracked their movements before and during the hunting season. They found two different 'personality' types: "bold runners," who ran a lot in open range; and "shy hiders," who kept a lower profile.

As expected, "shy hiders" were more likely to avoid hunters' gunsights, and survive. And that effect was strongest among young elk facing their first hunting season. Which suggests some genetic basis for their behavior, because the youngsters hadn't yet learned to fear human hunters.

Problem is, sitting still is a bad tactic for escaping wolves and grizzlies. So human hunters may actually be selecting for traits that make elk more vulnerable to their natural predators. Leaving them stuck between a rock and a hard place.